Thermos Bottle Buildings Roy Swain, P.E. Lyme Inn Radiant Floor - PowerPoint PPT Presentation

Thermos Bottle Buildings Roy Swain, P.E.

Lyme Inn

Radiant Floor

“Thermos Bottle” Building Design Heat Loss “Thermos Bottle” Building Design Heat Loss -10°F outside, 70°F Inside -10°F outside, 70°F Inside Building Element Heat Loss R-60 Roof 10% R-40 Walls (and Doors) 25% R-20 Basement/Foundation Walls 25% R-10 Basement Floor 5% R-5 Windows (10% of floor area) 35% Total 100% Approximate BTUH/ Sq. Ft. 5 For typical 150 Sq. Ft. Room: 750 BTUH (Hair Dryer on “Low”) Note: Excludes infiltration/ventilation

“Thermos Bottle” Building Design Internal Heat Gain Per Person 0-150 Sq. Ft./Person Heat Source Btuh/Person Body Heat (Sensible) 250 Lights* 400 Plug Loads** 400 Total 1050 *0.75 Watts/Sq. Ft. x 150 Sq. Ft. x 3.412 Btuh/Watt (=384) ** Wilkins and Hosni, Plug Load Design Factors (ASHRAE Journal, May 2011, P. 30.

Ventilation Air for One Person 15 cfm/ x 1.08 = 16 Btuh 300 Btuh net heat gain = ~20°F 16 Btuh/°F Therefore at -10°F outside air the 15 cfm of ventilation air needs to be at 55°F (!) to balance out the net heat gain assuming 75°F inside. And assuming zero solar heat gain through the windows.

Economizer Cooling Per person, ignoring heat loss, at 150 Sq. Ft. / Person Q = CFM x 1.08 x ΔT For 1050 Btuh/person heat gain: For 20°F ΔT = 50 CFM ● – Or 1/3 CFM per Sq. Ft. For 10°F ΔT = 100 CFM ● – Or 2/3 CFM per Sq. Ft. For 5°F ΔT = 200 CFM ● – Or 1-1/3 CFM per Sq. Ft.